A spyware tries to break into a system by trying at most 1 million combinations. What is the probability of it breaking in if the password is 1 (a) a combination of 6 different lower-case letters (b) a combination of 6 different upper- and lower-case letters (case sensitive) (c) a combination of any 6 upper- and lower-case letters (case sensitive) (d) a combination of any 6 characters (letters and digits)